(a) Field of the Invention
The present invention relates to a base station transmitting and receiving antenna and a control method thereof. Particularly, the present invention relates to base station transmitting and receiving antennas and control methods thereof that are capable of reducing installation and operation costs of a base station system.
The present invention was supported by the IT R&D program of MIC/IITA [2007-F-041-01, Intelligent Antenna Technology Development].
(b) Description of the Related Art
Base stations provide voice and data services to terminals located in allocated cell regions.
Power control of the base stations is an important element, which is needed to maximally set the amount of transmitted and received data as well as a level of a service quality with terminals. For power control, a code division multiple access (CDMA) technology has mainly been used in recent years. The CDMA technology uses an active power control method that performs forward and backward link power control on the basis of open-loop power control and closed-loop power control.
The active power control method performs a control operation such that a sum between power of a base station received from terminals and power transmitted from the base station to the terminals is maintained at a predetermined value, which will be described below with reference to FIGS. 1 and 2.
FIG. 1 is a schematic diagram illustrating a basic principle of power control of a base station using an active power control method.
As shown in FIG. 1, since a terminal A is located closer to a base station than a terminal B, the intensity of a signal that the base station receives from the terminal A is stronger than the intensity of a signal that the base station receives from the terminal B. At this time, the base station uses the active power control method to perform a control operation such that the intensity of a signal transmitted to the terminal B is stronger than the intensity of a signal transmitted to the terminal A, thereby allowing transmitted/received power between the base station and the terminal A to be the same as transmitted/received power between the base station and the terminal B.
FIG. 2 is a diagram illustrating an example of active power control that allows a sum between power transmitted from a terminal to a base station and power of the terminal received from the base station to be maintained at a predetermined value. For reference, in FIG. 2, PMS indicates transmission power that a terminal transmits to a base station, and PBS indicates reception power that the terminal receives from the base station.
As shown in FIG. 2, a sum between transmission power transmitted from a terminal to a base station and reception power of the terminal received from the base station is maintained at a value of −75 dBm. At this time, since the value of −75 dBm is only exemplary, the sum between the transmission power of the terminal and the reception power of the terminal may be set to be maintained at different values.
The power control of the base station using the active power control method that is shown in FIGS. 1 and 2 is applied to narrowband services, such as cellular services and personal communication services (PCS), and is effective in constantly maintaining a quality of service (hereinafter simply referred to as “QoS”) of voice and data between a base station and terminals.
Meanwhile, in the active power control method, when the terminals are located at a shadow region or an edge of a cell region or in a null region of a base station antenna radiation pattern, a large amount of power is required for signal transmission and reception between the base station and the terminals in order to maintain the QoS. A signal that is transmitted and received with a large amount of power increases interference noise in other terminals around a corresponding terminal to deteriorate the QoS, which results in compulsorily limiting signal transmission and reception with the terminals requiring a large amount of power.
In recent years, with the development of mobile communication technology, wideband services, such as a wideband code division multiple access (WCDMA), a high speed downlink packet access (HSDPA), and the wireless broadband Internet (Wibro), which provide moving picture data and voice services, have been provided. However, it is difficult to provide uniform QoS for wideband services to all terminals located in a base station cell, using only the active power control method.
The active power control method has a problem in that it becomes a factor making it difficult to establish a common base station that can provide two or more different services at the same time. That is, when a signal is transmitted from a base station to terminals using a wideband antenna for a common base station, a passive intermodulation noise of an antenna that is radiated at the time of transmitting the signal is input to a receiving antenna adjacent to a transmitting antenna, thereby considerably deteriorating signal reception performance. The deterioration in signal reception performance considerably deteriorates a QoS for various services that are provided from a base station to terminals located in a cell.
However, the common base station that can provide two or more different services at the same time has been increasingly required to reduce installation and operation costs of a base station system. Therefore, it is required to provide a power control method of a new base station that improves the existing active power control method.